2,3-Epoxypropyl neodecanoate, oligomeric reaction products with phosphorous acid

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August 2, 2016 to January 18, 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

water solubility: 2.7 mg/l

Analytical monitoring:

not required

Vehicle:

no

Details on test solutions:

The test item concentration were weighed out directly in Erlenmeyer flasks. Synthetic waste water according to OECD Guideline 209 was use as a nutrient solution and the 500 mL Erlenmeyer flasks were filled up to 250 ml with demineralised water. As a pretreatment, the test solution was stirred overnight. No pH adjustment was made. The flasks were aerated permanently to keep the dissolved oxygen concentration above 60 - 70 % saturation and to maintain the sludge flakes in suspension.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Activated sludge of a municipal sewage treatment plant (Hildesheim, Germany) was used.
Non-adapted activated sludge from this sewage plant at Hildesheim is well suited as it receives predominantly municipal sewage and hardly any industrial chemical waste. The sludge was washed twice with chlorine free tap water and adjusted to a dry sludge concentration of 3.0 g/L ± 10 %. The sludge was used within 24 h after sampling.
Dry sludge concentration 3.24 g/L, corresponding to 1.62 g/L in the test vessel

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

The temperature was determined in the measuring cell once during the measurement. The room temperature during the test was recorded continuously.
Nominal: 18 - 22 °C, actual: 21.4 °C

pH:

The pH value of the activated sludge was determined prior to test start. The pH value of the synthetic waste water was determined prior to use. Adjustment to 7.5 ± 0.5 was not necessary

Nominal and measured concentrations:

10 - 32 - 100 - 320 - 1000 mg/L were weighed out directly in Erlenmeyer flasks. As a pretreatment, the test solution was stirred overnight

Details on test conditions:

After 3 h incubation, the oxygen concentration of each control, reference item and test item replicate was determined by means of oximeter immediately after transferring the solution to the measuring cell and the oxygen depletion was recorded for at least 3 minutes on a flatbed recorder.

Reference substance (positive control):

yes

Remarks:

copper (II) sulphate pentahydrate

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

155 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

693 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

A preliminary tests (non GLP) was carried out with the concentrations of the test item of 10 – 100 – 1000 mg/L with two replicates each. The pH was measured in one replicate with 1000 mg/L test item. The flasks were aerated for 3 hours. In the preliminary test, additional replicates were prepared to determine the inhibition of nitrification. Two replicates 1000 mg/L were measured with addition of Allylthiourea ATU.

Based on the results the definitive study was carried out with 5 concentrations within the range 10 - 1000 mg/L in a geometrical series and with a dilution factor of 3.2. No pH adjustment was made. All concentrations were weighed out directly in the Erlenmeyer Flasks. Triplicates of the control without test item were included at the beginning and at the end of the test. The reference item was tested with three concentrations within the concentration range 58 - 180 mg/L and a dilution factor of 1.8

NOEC and EC-Values with Confidence Interval of the test item after 3 h exposure time, Inhibition of Total Respiration


EC-values [mg/L] Confidence interval
P = 95 [%] [mg/L]
NOEC* 10 ̶
EC10 155 114 – 198
EC20 284 256 – 307
EC50 693 578 – 796
EC80 > 1000 ̶

Results with reference substance (positive control):

In the reference test the EC50-value for copper (II) sulphate pentahydrate was determined by probit analysis with:
EC50 = 100 mg/L 95% Confidence Interval = 95.5 – 105 mg/L
This is in the recommended range of validity of 53 - 155 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

The mean specific oxygen uptake rate of the control replicates was 18.1 mg O2/g/h (validity criterion: should be > 20 mg O2/g/h). The oxygen uptake of activated sludge from municipal treatment plants is influenced by seasonal fluctuations and fluctuations in sewage flow etc. The lower oxygen uptake rate reflects the range of common uptake rates of activated sludge from municipal treatment plants and was considered to have no impact on quality and integrity of the study. Despite the lower respiration, the EC50-value of the reference item was in the required range. Therefore, no impact on the results of the test item can be expected through lower respiration.

The NOEC for the respiration inhibition test with the test substance is 10 mg test item/L. The EC10 is 155 mg test item /L and the EC50 is 693 mg test item /L

Executive summary:

A Respiration Inhibition Test with activated sludge according to OECD Guideline No. 209 was carried out with the test item. The test system was activated sludge of the municipal treatment plant of 31137 Hildesheim, Germany. The test was carried out under static conditions with the test item concentrations 10 - 32 - 100 - 320 - 1000 mg/L. The respiration rates of the control, reference and test item replicates were measured after a contact time of three hours, and the inhibitory effects of the test and reference item were determined in comparison to the control respiration rates. The mean inhibition of respiration for the test item replicates ranged from 3 % to 62 %.

In order to check the activity of the test system and the test conditions a reference test was carried out with copper (II) sulphate pentahydrate as reference item and the reference toxicity was determined. The EC₅₀-value for the reference item was 100 mg/L.

Description of key information

A Respiration Inhibition Test with activated sludge according to OECD Guideline No. 209 was carried out with the test item. The test system was activated sludge of the municipal treatment plant of Hildesheim, Germany. The test was carried out under static conditions with the test item concentrations 10 - 32 - 100 - 320 - 1000 mg/L. The respiration rates of the control, reference and test item replicates were measured after a contact time of three hours, and the inhibitory effects of the test and reference item were determined in comparison to the control respiration rates. The mean inhibition of respiration for the test item replicates ranged from 3 % to 62 %.

In order to check the activity of the test system and the test conditions a reference test was carried out with copper (II) sulphate pentahydrate as reference item and the reference toxicity was determined. The EC₅₀-value for the reference item was 100 mg/L. The NOEC for the respiration inhibition test with the test substance  is 10 mg test item/L. The EC10 is 155 mg test item /L and the EC50 is 693 mg test item /L

Key value for chemical safety assessment

EC50 for microorganisms:

693 mg/L

EC10 or NOEC for microorganisms:

155 mg/L